title: Radiometric-microbiologic assay fo vitamin B-6: analysis of plasma samples.
abstract: A radiometric microbiologic assay for the analysis of vitamin B-6 in plasma was developed. The method is based on the measurement of 14CO2 generated from the metabolism of DL-l-14C-valine (L-l-14C-valine) by Kloeckera brevis. The assay is specific for the biologically active forms of the vitamin, that is, pyridoxine, pyridoxal and pyridoxamine, and their respective phosphorylated forms. The biologically inert vitamin B-6 metabolite (4-pyridoxic acid) did not generate a response at concentrations tested. The radiometric technique was shown to be sensitive to the 1 nanogram level. Reproducibility and recovery studies gave good results. Fifteen plasma samples were assayed using the radiometric and turbidimetric techniques. The correlation coefficient was r = 0.98. Turbid material or precipitated debris did not interfere with the radiometric microbiologic assay, thus allowing for simplification of assay procedure.
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods*; D002245:Carbon Dioxide / Q000378:metabolism; D002250:Carbon Radioisotopes; D005260:Female; D006801:Humans; D008297:Male; D009391:Nephelometry and Turbidimetry; D011736:Pyridoxine / Q000097:blood*; D011817:Rabbits; D014633:Valine / Q000378:metabolism; D026681:Vitamin B 6 Deficiency / Q000097:blood; D015003:Yeasts / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D014633:Valine; D011736:Pyridoxine